In circuit design, a hysteresis comparator is generally used to eliminate interferences of some noise voltages lower than a threshold voltage. The hysteresis comparator generally comprises a first input terminal, a second input terminal and an output terminal. Of an input voltage Vp of the first input terminal and an input voltage Vn of the second input terminal, the output terminal outputs a corresponding logic high level or logic low level. The logic high level and the logic low level are relative, and generally, a level corresponding to the logic high level and a level corresponding to the logic low level are relative to the same reference level, and the level corresponding to the logic high level is higher than the level corresponding to the logic low level. For example, the level corresponding to the logic low level may be 0 V, relative to a ground level, and the level corresponding to the logic high level may be any voltage value (it should be a voltage value greater than 2.5 V in an actual circuit) greater than 0 V, relative to a ground point level.
The hysteresis comparator will generate a hysteresis voltage Vhy. Due to the generation of the hysteresis voltage Vhy, when Vp−Vn>VTRP+, the output terminal Vo outputs a logic high level, and when Vn−Vp<VTRP−, the output terminal Vo outputs a logic low level. It is assumed that a voltage output by the output terminal is Vo, and in this way, for the hysteresis comparator, the Vo will not turn between the logic high level and the logic low level at the instant of Vp=Vn. Vhy=VTRP+−VTRP−. Generally, the VTRP+ is a positive threshold voltage; the VTRP− is a negative threshold voltage; and the Vhy is a difference obtained by subtracting the negative threshold voltage from the positive threshold voltage. The VTRP+ and the VTRP− are two threshold values for performing voltage comparison.
For an ideal hysteresis comparator, the hysteresis voltage thereof should not be affected by factors such as the temperature or the manufacturing processes of electronic elements, and a stable hysteresis voltage should be provided regardless of the working environment, thereby ensuring the stability and precision of the work performance of the hysteresis comparison circuit. Moreover, hysteresis voltages of hysteresis comparators of the same model generated by the same batch have a small variance, thereby ensuring the stability and precision of products in a batch production.